1. Technical Field
System and method for monitoring the state of health of a power electronic system.
2. Background Art
Power conversion systems, such as median electric power conversion systems and motor drive systems, have gained increasing attention in automotive applications. Power conversion systems typically include various power semiconductor devices, such as a power switch. The power switch may include a diode and an insulated gate bipolar transistor (IGBT). Many of these semiconductor devices switch hundreds amperes (A) and hundreds volts (V) at a high rate, often in the tens of kilohertz (kHz). During these switching operations, the semiconductor device may dissipate a large amount of heat on order of kilowatts (kWs). Furthermore, the large amount of heat can degrade the semiconductor device and cause the semiconductor device to reach a high temperature. The high temperature of the semiconductor device can cause the semiconductor device to be degraded or fail unless the semiconductor device is cooled to a lower temperature.
Various materials can be used to fabricate the semiconductor device. However, the efficiency and effectiveness of the material may be limited to various operating temperatures due to inherent properties of the material. If the material used to fabricate the semiconductor device overheats, the semiconductor device may degrade or fail unless the semiconductor device is cooled to a lower temperature. In addition, a degrading or failure of the semiconductor device can cause a power conversion system in an automotive vehicle to degrade or fail.
Many factors can impede or degrade the performance of the semiconductor device. For example, high electrical stress or large temperature excursion can reduce the performance of the semiconductor device or a module of which it is a part. As the temperature of the semiconductor device increases, the performance of the semiconductor device may be reduced.
Various electronic devices have been used to measure the temperature of a semiconductor device. For example, a thermocouple, a thermistor, or an optical thermal sensor have been used as temperature sensors in semiconductor modules. However, these devices used as temperature sensors have provided neither an in situ nor an instantaneous response.
Furthermore, inherent electrical temperature-sensitive parameters (TSPs) in various electronic devices have been used to determine the temperature of the semiconductor device. TSPs may include a voltage drop, saturation voltage, and gate threshold voltage of the semiconductor device. For example, the semiconductor device may be a diode, a bipolar transistor, an IGBT, or a field-effect transistor (FET). Using the TSPs, the temperature of the semiconductor device can be calculated and the thermal performance of the semiconductor device can be deduced. However, TSPs depend significantly on the operating conditions of the semiconductor device and typically require measuring multiple factors that affect the operation of the semiconductor device. For example, voltages of semiconductor devices depend greatly on the operation conditions, such as current, bias, and dynamic transitions. In addition, interaction of cascaded subsystems may cause a measurement of a TSP in a semiconductor device to be inaccurate.